A code screen starts with applicability, not arithmetic

A correct multiplication can still produce the wrong decision if it uses an ineligible space. Apply the complete supplied rule before calculating the limit.

Original case · Suggested 18 minutes · Edition 2026-10-12.1

By the end of this workshop

Choose a method that respects the supplied conditions.
Explain how a changed condition affects the decision.
Identify a physical or procedural cross-check and an applicability limit.
Record the assumption you would verify next time.

Start with the complete model

Givens and assumptions

Original practice criterion, not an asserted ASHRAE code extract: compare the entire 26 lb charge with 0.0090 lb/ft³ times eligible room volume.
Main room is 2,800 ft³. Adjacent room is 200 ft³. Credit the adjacent room only when a permanently open connection is verified; a normally closed door does not qualify in this supplied criterion.
The current connection is a normally closed door. No mitigation or other volume credit is permitted.

Study calculator, scratch notepad and whiteboard

Expression Trigonometry in degrees

Supports +, −, *, /, ^, parentheses, sqrt, abs, log (base 10), ln, sin, cos, tan, pi and e. Confirm units independently.

Scratch notepad

Scratch text and drawings stay in this tab and clear when you leave or reload. Save important reasoning in a response or reflection below before leaving.

Scratch whiteboard

Sketch a control volume or air path with a mouse, pen or touch. Ink stays in this page session and clears on reload. Use the response and reflection fields as a keyboard alternative. Sign in before starting and save a reflection to retain your reasoning.

1 · Choose the method

For the supplied 26 lb charge and normally closed adjacent-room door, which screening decision follows?

Choose one responseCredit both rooms automatically and approve 27 lb.Compare 26 lb with the volume in ft³ directly.Eligible volume 2,800 ft³ permits 25.2 lb; the proposal fails.Approve because a normally closed door can sometimes be opened.

ConfidenceWhy did you choose this method? Optional personal reasoning, up to 1,000 characters.

2 · Change the condition

Predict before you inspect the calculation.

The connection is redesigned and verified permanently open under the supplied criterion.

Main room 2,800 ft³ plus adjacent room 200 ft³, permanently open connection verified, entire charge 26 lb, original practice limit 0.0090 lb/ft³, no other credits.

Check the first decision to open the changed-condition response.

Personal notes are not automatically graded. Workshops are linked learning experiments, separate from timed diagnostics and mocks. They do not predict a pass or award instructional hours.

Reference navigation drill

Search concept: refrigerant safety, codes and standards

Separate a safety classification, an applicability condition and a quantitative limit. Verify what the authorized handbook contains rather than assuming every rule is embedded.

Use an authorized reference. A search term does not guarantee that a current examination reference contains every relationship used in this teaching case.

Where this model stops

All concentration and connection criteria here are original hypothetical givens. They are not a current-code quotation, compliance certificate or assertion that these rules appear in the examination handbook.

The PE Mechanical: HVAC and Refrigeration examination uses the NCEES PE Mechanical Reference Handbook. These source links provide study context; they are not additional exam-day references.

NCEES · current PE Mechanical: HVAC and Refrigeration specification ↗

Found an unclear condition or calculation? Include workshop applicability-before-volume and the step in your comment.

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